ὅτι αἷμα ἁγίων καὶ προφητῶν ἐξέχεαν, καὶ αἷμα αὐτοῖς ἔδωκας πιεῖν· ἄξιοί εἰσιν.
for they have poured out the blood of saints and prophets, and thou hast given them blood to drink; they are worthy.

How is the "ἄξιοί εἰσιν" connected to the text before? Are the saints or prophets worthy of getting a revenge or are the evil doers deserving to be judged? In John ἄξιος is positive (throughout Revelation), one example is negative and points towards a revenge motive "ἄξια γὰρ ὧν ἐπράξαμεν ἀπολαμβάνομεν" ( for we receive the just recompense of what we have done" (Luk 23,41).

I put it in the discourse section as it is not mainly a grammatical/syntactical issue, I think, but a matter of pragmatics and discourse. I think grammar alone is not giving an answer here.

For the rendering in a translation I would leave that decision open - but what would one write in a commentary? Peter